It is conventionally known that a chargeable and dischargeable secondary battery (hereinafter referred to as the battery) is used as a motor power supply for electric vehicle and hybrid vehicle which use an electric drive motor as a vehicle drive source. Decrease of temperature in the battery deteriorates its charge-discharge characteristics. Therefore, it is preferable to warm up the battery when a vehicle is in a cold start state, namely, when the vehicle is restarted after long hours of rest at a place where outdoor temperature is low, for instance, in winter or in cold climates.
As a prior art for battery warm-up, for example in a hybrid vehicle with an internal combustion engine and an electric drive motor as vehicle drive sources, JP 2001197607A (Patent Document 1) discloses that, when the battery is required to be warmed up, the warm-up for the battery is executed by feeding a motor driving current (a so-called d-axis current or magnetic flux component current) through the electric drive motor in only d-axis by using vector control of an electric drive motor-control device. The d-axis current is a current flowing in a direction of strengthening a magnetic flux of a permanent magnet of a motor rotor. In other words, according to such a technique, electrical power of the battery is consumed without rotating the electric drive motor and thereby can warm up the battery by allowing the battery to discharge for heat generation purposes. The prior art is to be used for only hybrid vehicle which has the two of an electric drive motor and an internal combustion engine as drive sources of the vehicle and is capable of running by at least one of these two drive sources. That is, in the prior art, the battery is warmed up by feeding the d-axis current for vector control through the electric drive motor, while the internal combustion engine is warmed up by its own power, and thereby a vehicle driving with the internal combustion engine warm-up and the battery warm-up are performed at the same time.
Meanwhile, the battery warm-up operation (cold start operation) described in Patent Document 1 is not applicable for so-called electric vehicles which uses only an electric drive motor as a vehicle drive source. The reason is that Patent document 1 is predicated on using the two of the internal combustion engine operation by itself and the battery warm-up operation by feeding the d-axis current for the electric drive motor during a cold start of vehicle. More in detail, if adopting the technology of Patent Document 1 to the electric vehicle, only the d-axis current for vector control is since fed through the electric drive motor during a cold start operation (in a situation where battery warm-up is required), it is difficult to perform both the vehicle driving mode and the battery warm-up mode by using the electric motor at the same time. Namely, if adopting the technology of Patent Document 1 to the electric vehicle, the battery warm-up technology is applicable to a situation where the vehicle is stopped, but, in a driving mode (in a mode in which a required drive torque for the motor is generated through an accelerator) at a vehicle cold start, required is since a q-axis current (torque component current), it is difficult to make a situation of using only the d-axis current for the battery warm-up operation. On the other hand, when considering as to the hybrid vehicle, the vehicle is driven exclusively by the internal combustion engine during the battery warm-up operation while only the d-axis current is fed to the electric drive motor (the q-axis current is zero so that the drive motor does not rotate). Consequently, from the view-point of environmental considerations such as emissions reduction, the hybrid vehicle does not make full use of its abilities.
The present invention is invented in view of the above circumstances, and its object is to provide a control device for vehicle electric drive motor capable of addressing the above-described matters thereby to realize a speedup of battery warm-up and take the environmental considerations into account regardless of an electric vehicle or a hybrid vehicle. The present invention also is to provide a vehicle with such a control device for an electric motor as vehicle drive motor.